Cell Selection With UE Capability and Supplementary Uplink
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Solution Overview
Problem
The asymmetry/imbalance between NR downlink and uplink coverages in wireless communication systems, particularly in TDD deployments for the 3.5 GHz NR band, results in UEs being unable to successfully transmit UL communications, leading to poor UL resource utilization and challenging cell measurement and selection when supplementary uplink (SUL) is in place.
Innovation Solution
A method for user equipment (UE) to receive cell selection information and perform measurements on both a primary and supplementary carrier, determining appropriate cell selection based on its capability to communicate using the supplementary uplink, and adjust cell selection criteria with an offset to include SUL information, enabling improved UL coverage through carrier aggregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a UE operates on a single UL carrier (first carrier) for NR communication, then the device complexity is reduced and operation is simpler, but the uplink coverage is insufficient and UL resource utilization is poor due to asymmetry between NR downlink and uplink coverages
Solution Approach 1:
The patent combines NR first carrier and LTE second carrier through carrier aggregation to form a supplementary uplink (SUL) configuration. The UE can utilize both carriers simultaneously for uplink transmission, merging their resources to overcome the coverage limitation of the NR first carrier alone while maintaining operational simplicity through standardized aggregation procedures.
Solution Approach 2:
The LTE second carrier is configured to serve dual purposes: it functions as a standalone LTE carrier for LTE-only UEs and as a supplementary uplink carrier for NR UEs. This multi-functionality allows the same carrier to improve UL coverage for NR UEs without compromising LTE service continuity, thereby enhancing reliability without adding dedicated infrastructure.
2Reliability
If a supplementary uplink (SUL) carrier is introduced to improve UL coverage, then uplink coverage and resource utilization are enhanced, but the cell selection process becomes more complex and difficult to measure
Solution Approach 1:
The base station pre-configures the UE with cell selection parameters for both the first NR carrier and the second LTE carrier before the UE performs cell selection. This preliminary provision of measurement parameters and selection criteria enables the UE to evaluate both carriers systematically without encountering complexity during the actual selection process, as all necessary information is prepared in advance.
Solution Approach 2:
The base station acts as an intermediary by providing detailed cell selection information and measurement configurations to the UE. This intermediary role simplifies the UE's task by translating the complex multi-carrier selection problem into a standardized measurement and reporting process, where the base station processes the complexity and returns simplified selection guidance to the UE.
3Measurement precision
If cell selection parameters are adjusted with offsets to account for SUL capability, then cell selection accuracy is improved, but the measurement and evaluation process requires additional parameters and becomes more complex
Solution Approach 1:
The patent introduces offset parameters (such as q offsets) that are applied to the cell selection evaluation of the second LTE carrier based on the UE's SUL capability and the measured signal quality. These parameter changes enable dynamic adjustment of selection criteria to reflect the actual UL coverage conditions, improving measurement precision by accounting for the asymmetry between DL and UL coverages without requiring fundamentally new measurement mechanisms.
Data Source
AI summary
A cellular communication system is disclosed in which a base station operates a cell which has a supplementary uplink portion (e.g. on a different frequency and/or using a different technology). The base station broadcasts an offset for user equipment (UE) in its coverage area to assist the UE performing cell selection. Specifically, the UE determines, based on measurements for the cell, the offset, and capability of the UE to communicate using the supplementary uplink portion, whether the cell of the base station is an appropriate candidate for cell selection such that: if the UE is capable of communicating using the supplementary uplink portion then the UE performs cell (re)selection based on the offset; and if the UE is not capable of communicating using the supplementary uplink portion then the UE disregards the offset in its cell (re)selection.